The present invention relates to a measuring device for determining salt concentration in water and more particularly to a device for measuring the variation of mass density along a vertical line.
One accurate and convenient way of measuring salt concentration in water is to measure the electrical conductivity of the solution. Various types of instruments are available for measuring conductivity of fluids. For example, in U.S. Pat. No. 3,748,899, entitled "Conductivity And Temperature Sensing Probe", which issued Jul. 31, 1973, to Michael C. Gregg and Charles S. Cox, there is shown and described a probe for measuring the vertical profile of temperature and salinity in the ocean. In this patented device, sensing means are provided consisting of a pair of inner and outer electrodes which are employed to determine voltage variations across a small chamber opening, these variations being due to fluctuations in electrical resistance which in turn is related to the temperature and salinity of the ocean medium. To provide the voltage for this sensing means, a separate driving means, such as a pair of electrodes, are used to apply a constant amplitude electrical current across the opening, the sensing means measuring the variations in this constant amplitude.
While instruments developed for ocean measurements, such as the one described in U.S. Pat. No. 3,748,899, can measure the vertical profile of temperature and salinity, these heretofore available devices do not provide sufficient resolution required by a laboratory instrument which required resolution is less than 1 mm in the vertical direction.